I. Technical Field
The present invention relates to a thermostat apparatus which automatically controls a temperature of a coolant mainly cooling the engine of an automobile.
II. Description of the Related Art
A conventional thermostat apparatus 20, as shown in FIG. 7, has a housing body 16 including a radiator coupling port 2 to let a low-temperature coolant A, cooled by a radiator or the like, flow into a housing body interior 19, a bypass port 3 to let a high-temperature coolant B, heated by the engine, flow into the housing body interior 19, and an engine coupling port 4 to feed out a coolant C, which is a mixture of the coolants flowing through the radiator coupling port 2 and the bypass port 3, to the engine.
The thermostat apparatus 20 also includes a temperature sensitive movable part 8 or a thermally expanding element which moves according to a liquid temperature in the housing body interior 19, a piston shaft 7 which has one end retained in the temperature sensitive movable part 8 and slides in response to thermal expansion or contraction of the thermal extension body, a piston shaft support 6 provided on a radiator coupling port 2 side to support the other end of the piston shaft 7, a main valve 9 which moves together with the temperature sensitive movable part 8 to control the flow-in amount of the low-temperature coolant A into the housing body interior 19 through the radiator coupling port 2, a frame 10 supported by a housing cover 1, a main spring 11 which is provided between the main valve 9 and the frame 10 in a compressed state and urges the main valve 9 toward the radiator coupling port 2, a bypass shaft 12 provided in a direction toward the bypass port 3 from the temperature sensitive movable part 8, a bypass valve 13 which is provided at the bypass shaft 12 and controls the flow-in amount of the high-temperature coolant B into the housing body interior 19 through the bypass port 3, and a bypass spring 14 which is provided between the bypass valve 13 and the temperature sensitive movable part 8 in a compressed state and urges the bypass valve 13 toward the bypass port 3.
When the liquid temperature around the temperature sensitive movable part 8 rises, the thermal extension body sealed in a cup 15 is thermally expanded to push the piston shaft 7. This causes an opening movement of the main valve 9 together with the temperature sensitive movable part 8 against the load of the main spring 11, increasing the flow-in amount of the low-temperature coolant A, and causes a closing movement of the bypass valve 13, reducing the flow-in amount of the high-temperature coolant B.
When the liquid temperature around the temperature sensitive movable part 8 falls, contraction of the thermal extension body occurs, so that the urging force of the main spring 11 pushes back the piston shaft 7, causing the closing movement of the main valve 9 to decrease the flow-in amount of the low-temperature coolant A from the radiator, and increasing the flow-in amount of the high-temperature coolant B.
Through such an operation, the conventional thermostat apparatus 20 detects mainly the liquid temperature of the coolant C or a mixture of the high-temperature coolant B and the low-temperature coolant A from the radiator, controls it, and feeds the coolant C to the engine.
Thermostat apparatuses which have similar configurations and perform similar operations or techniques are disclosed in Japanese Unexamined Utility Model Publication No. Hei 2-5672, Japanese Unexamined Utility Model Publication No. Hei 6-37524, Japanese Unexamined Patent Publication No. Hei 10-19160, Japanese Patent Publication No. Sho 47-16584 and Japanese Unexamined Utility Model Publication No. Sho 61-175534 are proposed.
Japanese Unexamined Utility Model Publication No. Sho 61-175534 discloses the structure such that a coolant guiding cylinder is attached to the foregoing so-called bottom bypass type thermostat so that the coolant from the bypass is guided to the periphery of the temperature sensitive movable part.